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Microcontrollers

DIY Biotech: A Spectrophotometer for Measuring Bacterial Growth

Build an Arduino-based spectrophotometer to explore how the optical density of bacteria suspended in a liquid can be used to measure the rate and stage of bacteria growth.

Libraries and Headers in C: A Tutorial

If you’ve written a program for a microcontroller board such as the Arduino, Raspberry Pi, or Propeller QuickStart, you have relied on software libraries that provide constants and functions.  Often, we use software libraries without thinking much about them.

When you start to write libraries, it takes time to read documents, follow directions, and experiment with simple functions. Fortunately, after you understand how to create libraries and header files for the software tools you use, you'll have a useful skill that can simplify programming tasks.

Even if you never create a library, you probably want to know how they work and what they contain. This tutorial provides information that gives you a good start.

Build the Graphing Thermometer

Recently, I began to explore ways to improve and upgrade my “thermal monitoring technology” and came up with this simple, easy to build trend-plotting thermometer. This project features a large color graphics display to show the current temperature in big bold digits. Better than that, it also graphs the temperature trends over the most recent 4, 8, 16, or 24 hour period. 

Whether it be temperature trends, time and date, current/voltage readings, battery status, or other variables, consider giving your next project some extra pizazz by including an LCD color graphics display into the design!

An ESP8266 Live Wi-Fi Webcam

Having read about the ESP8266 NTP clock in previous issues of Nuts & Volts, an idea came to mind to construct an interface camera using the ESP8266. In this project, we used an old Android phone as a camera source and linked to an ESP8266 based webserver. The phone acts as a camera server and the ESP8266 web server acts as a client to the camera server. The webserver displays the live webcam on its web page.

Build the Laser Pencil Engraver

Several months ago, an idea popped into my head for a fun project. I wondered if I could burn some characters into the yellow paint of a No. 2 pencil with one of those powerful diode lasers available on eBay. Perhaps it could be my name or my grandkid’s names, or even a happy birthday message to my lovely wife. Here’s how I did it.

Build an Internet Digital Clock

The advent of the ESP32 Wi-Fi development boards allows for an increase in the sophistication of a digital clock. It doesn’t take much imagination to envision a digital clock with a large LCD display to not only show the usual time, date, temperature, and humidity, but to also be able to retrieve things from the Internet like the weather or weather forecast, and stock market reports as well. This seven inch clock also automatically corrects for Daylight Savings Time.

TGI: The TEENSY Graphics Interface

The February and March 2018 editions of Nuts & Volts featured my article detailing the Arduino Graphics Interface (AGI) project which described a general-purpose hardware and software platform that could draw graphical objects onto the face of any analog oscilloscope. A reader challenged me to see if the AGI concept and software library could be ported to the newer and faster TEENSY 3.6 processor. This article describes the new and improved TEENSY Graphics Interface project that implements a fully operational “CRT Clock” as a working demonstration of a TEENSY based graphics platform.

Build a MIDI Autoharp

This project is a follow-on from my MIDI lyre project featured in the July-August magazine. I’m going to describe how to build a MIDI autoharp. Like the lyre, this is a MIDI controller, so it doesn’t make any sounds itself. Instead, it sends MIDI messages to an external synthesizer. It’s the synthesizer that makes the sounds.

Create an LED Sign Controller

When you plan to create a large sign with LED dot-matrix modules, the circuits and software can seem like a big challenge. However, the step-by-step approach in this tutorial gives you what you need to know to make a sign of your own.

Keep Your Home Secure with Raspberry Pi

Surveillance is one of the most effective deterrents against crimes lke burglary and theft. The Raspberry Pi can be the foundation of a great DIY home security system.